Isolation of Zucchini Heteropolymeric Pectin and Preliminary Study on Its Hypoglycemic Activity

To promote the deep processing of zucchini, heteropolymeric pectin fractions from zucchini was analyzed and their hypoglycemic activity was explored. Combining acid and base treatment, two pectin fractions were isolated, namely zucchini acid-extracted pectin (ZPA) and zucchini alkali-extracted pectin (ZPB). The yield, composition, and structural properties of two fractions were analyzed. Moreover, high-fat diet induced bumblebee diabetic model was established to explore the hypoglycemic activity of zucchini pectin. Results showed that the yield of ZPB was 2.45 times higher than that of ZPA. ZPA had an averaged molecular weight of 70297 Da and polydispersity index of 1.149, while ZPB had an averaged molecular weight of 126170 Da and polydispersity index of 1.677, indicating the more complex components of ZPB. Monosaccharides including arabinose, galactose, galacturonic acid, glucuronic acid, rhamnose, and mannose were found in both ZPA and ZPB, while glucose and ribose were only present in ZPA. It indicated that ZPA and ZPB were heteropolymeric pectins containing RG-I structure. ZPA had less but longer RG-I side chain, whereas ZPB had more and shorter RG-I side chain. Based on bumblebee diabetic model, ZPA and ZPB were found to significantly lower the blood glucose and trehalose level, indicating that zucchini pectin had potential hypoglycemic activity.